The present invention relates to an optical axis monitoring system, and more particularly to an optical axis monitoring system for monitoring deviations in the alignment of the optical axis of a light beam in an optical apparatus.
In a conventional apparatus of this type, a light detecting element has been disposed in a path of a light beam from a light source. That is, the light beam is directly received onto a light-sensing surface of the light detecting element so that the light beam is intercepted by the light receptive element. The presence of the light detecting element directly in the optical path greatly restricts the freedom of design of the apparatus, often making it bulky.